The present invention relates to an antistatic organopolysiloxane composition or, more particularly, to an organopolysiloxane composition capable of giving a cured silicone rubber which is outstandingly free from the problem of accumulation of static electricity over a long period of time even at a relatively high temperature.
Needless to say, the problem of static electricity accumulated on fibers, plastics, rubbers and the like polymeric materials presents a very serious drawback in a variety of fields not only in respect of attraction of dusts and danger of possible explosion due to the spark discharge of the accumulated electricity but also in respect of the possible error in precision electronic instruments due to the strong electric fields around the charged surface. Accordingly, various attempts and proposals have been made to reduce accumulation of static electricity in the industries in which these materials are involved.
For example, various kinds of antistatic agents are proposed which are used either by being incorporated into the polymeric material before it is shaped into the form of fibers or plastic or rubber articles or by being applied on to the surface thereof. Compounds useful as such antistatic agents of internal and external uses include anionic ones, e.g. salts of carboxylic acids and phosphoric acid derivatives, cationic ones, e.g. amines and quaternary ammonium salts, and non-ionic ones, e.g. polyhydric alcohols.
These conventional antistatic agents are indeed effective in so far as the polymeric materials incorporated or coated therewith are used at room temperature or therearound. However, when the temperature is high at 150.degree. to 300.degree. C., for example, the antistatic performance of these antistatic agents is rapidly lost within a relatively short time. When the polymeric material into which these antistatic agents are incorporated is a silicone rubber, moreover, the antistatic agent is very detrimental to the properties of the cured silicone rubber article, in particular, in respect of the increase in the permanent compression set. The effect of the external application of an antistatic agent is rather temporary even at room temperature.
Despite the above mentioned problem, it is conventional that a silicone rubber compound is formulated with an antistatic agent as mentioned above in certain applications. For example, most of the fixing rollers in dry-process photocopying machines are made of a silicone rubber in view of the excellent heat resistance of silicone rubbers in comparison with other organic rubbers while the high electric insulation of a silicone rubber having a volume resistivity of, for example, 10.sup.14 ohm.cm or higher causes serious troubles due to the static electricity induced by the rubbing action between rollers that the paper fed to the roller sometimes winds around the roller or the toner particles are displaced from their correct positions in the course of fixing to cause blur of the photocopied images. Therefore, it is almost indispensable to incorporate an antistatic agent into silicone rubber compounds used for fabrication of fixing rollers of photocopying machines while the antistatic effect is rapidly lost at an elevated temperature of, for example, 180.degree. to 230.degree. C. to which the fixing rollers are not rarely heated when the photocopying machine is run continuously.